1. Field of the Invention
The invention in general relates to semiconductor cooling, and more particularly to an improved cooling arrangement for high power semiconductor devices.
2. Description of Related Art
During operation, semiconductor circuits generate heat, particularly high power semiconductor switching devices as may be used in ac to dc or dc to ac power conversion equipment.
The power density in these semiconductor circuits is limited by the ability to provide adequate cooling. With improved cooling, the power density can be significantly increased thus allowing for a reduced amount of semiconductor material and a substantial cost savings. In addition, the improved cooling results in a longer thermal cycle life for the semiconductors and a higher reliability for the switching circuitry.
Presently used cooling arrangements include the use of a liquid cooled metallic heat sink to which a semiconductor package is mounted. Heat generated during operation of the circuitry is conducted to the bottom surface of the package, and then to the liquid cooled heat sink. This arrangement however suffers from an objectionably high thermal resistance not only through the semiconductor package but also across the package-heat sink interface.
Certain other cooling arrangements bond a common planar electrode of the semiconductor circuit directly to an electrically insulating, thermally conducting ceramic member such as aluminum oxide, aluminum nitride or beryllium oxide, by way of example. The ceramic member in turn is coupled to a liquid cooled heat sink. Although this arrangement provides satisfactory cooling, an even more efficient improved cooling arrangement would provide for a more economical system. The present invention provides such improved arrangement.